The present invention relates to an apparatus and method for performing diskectomy and more particularly to an instrument for performing partial diskectomies utilizing minimally invasive surgical techniques and a method for using the instrument.
Referring to prior art FIGS. 9 and 10, the spine 120, also known as the vertebral column or the spinal column, is a flexible column of vertebrae 100 (special types of bones) held together by muscles, ligaments and tendons. The spine 120 extends from the cranium (not shown) to the coccyx 126, encasing a spinal cord 128 and forming the supporting axis of the body (not shown). The spinal cord 128 is a thick bundle of nerve tissue (nerves) that branch off to various areas of the body for the purposes of motor control, sensation, and the like. The spine 120 includes seven cervical vertebrae (not shown), twelve thoracic vertebrae (not shown), five lumbar vertebrae, LI-LV, five sacral vertebrae, SI-SV, and three coccyx vertebrae 126. The sacral and coccyx vertebrae are each fused, thereby functioning as a single unit. FIG. 10 shows the lumbar region 122, the sacral region 124 and the coccyx 126 of the spine 120 and that the vertebrae 100 are stacked one upon another. The top portion 100a and bottom portion 100b of each vertebrae 100 is slightly concave. The opposing concave vertebral surfaces form the intervertebral space 121 in which an intervertebral disk (not shown) resides. Each of the intervertebral disks has a soft core referred to as a nucleus pulposus or nucleus (not shown).
In FIG. 9, directional arrow 101a is pointing in the posterior direction and directional arrow 101b is pointing in the anterior direction. FIG. 9 shows that each vertebrae 100 includes a body 106 in the innermost portion, a spinal canal 108 and a spinous process 102 at the posterior-most end of the vertebra 100. The vertebrae 100 are substantially similar in composition, but vary in size from the larger lumbar to the smallest coccyx vertebrae 126. Each vertebrae 100 further includes two transverse processes 104 located on either side and a protective plate-like structure referred to as a lamina 110. Nerves from the spinal cord 128 pass through the spinal canal 108 and foramina 111 to reach their respective destinations within the body.
The natural aging process can cause a deterioration of the intervertebral disks, and therefore, their intrinsic support strength and stability is diminished. Sudden movements may cause a disk to rupture or herniate. A herniation of the disk is primarily a problem when the nucleus pulposus protrudes or ruptures into the spinal canal 108 placing pressure on nerves which in turn causes spasms, tingling, numbness, and/or pain in one or more parts of the body, depending on the nerves involved. Further deterioration of the disk can cause the damaged disk to lose height and as bone spurs develop on the vertebrae 100, result in a narrowing of the spinal canal 108 and foramen 111, and thereby causes pressure on the nerves emanating from the spinal cord 128.
Presently, there are several techniques, in addition to non-surgical treatments, for relieving the symptoms related to intervertebral disk deterioration. Surgical options include chemonucleolysis, laminectomy, diskectomy, microdiskectomy, and spinal fusion.
Chemonucleolysis is the injection of an enzyme, such as chymopapain, into the disk to dissolve the protruding nucleus pulposus. The enzyme is a protein-digesting enzyme and is used to dissolve the disk material. Since the enzyme is essentially a tissue-dissolving agent, it is indiscriminate in the protein-based matter it dissolves. Should the enzyme be injected into the wrong place, or if there is a breach in the disk capsule that would allow the solution to enter the spinal canal or to contact nerve tissue or the like, the resultant damage to nerve tissue could not be reversed. Even worse, about half of the patients who receive chemonucleolysis treatments experience increased back pain and muscle spasms immediately after the injection and more than half have incapacitating back pain for durations up to three months after such treatments.
A laminectomy is performed to decompress the spinal canal 108 by open surgical techniques under general anesthesia. In this procedure, the lamina 110, (the bone that curves around and covers the spinal canal 108 as shown in FIG. 9), and any disk tissue causing pressure on a nerve or the spinal canal 108, are partially removed. This technique is highly invasive and traumatic to the body, and therefore requires an extended recovery time of about five weeks and a hospital stay of a few days. In addition to the trauma inflicted on the body from even a successful surgery, there are increased risks of future problems due to the removed portion of the lamina 110 which is no longer in place to support and protect the spinal canal 108 at the area where the surgery took place. Further, the vertebrae 100 may shift due to the lack of support in the structure. Thus, simply removing the disk and parts of the vertebral bone is a short-term, pain-relieving corrective action but not a long-term solution.
Diskectomy is a form of spinal surgery wherein part or all of an intervertebral disk is excised typically through open surgical techniques. Recently, less invasive techniques referred to as percutaneous diskectomy or microdiskectomy have been developed to reduce the surgical trauma to the patient. In microdiskectomy, a much smaller incision is made than in normal open surgeries. A small retractor, working channel or tube is inserted through the posterior muscles (not shown) to allow access to the damaged or herniated disk. Surgeons utilize special surgical instruments modified to work in such small openings such as curettes, osteotomes, reamers, probes, retractors, forceps, and the like to cut and remove part of the disk while monitoring their technique using a microscope, fluoroscope (real-time X-ray monitoring), and/or an endoscope (a miniature TV camera with associated viewing monitor). While this technique is much less invasive than conventional open surgeries, due to their design the instruments presently available tend to extend the length of time of the surgery and may cause possible damage to areas other than the herniated disk. For example, the curette is a spoon-shaped instrument with a sharp edge that is used mainly to scrape the nucleus pulposus matter (not shown) from the end plates of the vertebral bones. Since the blade is unprotected, there is potential for damage to the surrounding nerves and ligaments during insertion and during use. Further, due to the varying concavity of the vertebral space (or the concavity of the top and bottom portions 100a,b of the vertebral bones) it is often a time consuming procedure for the surgeon to repeatedly scrape at varying angles using the curette. Another instrument that is often used is the reamer (not shown) which is intended to remove the nucleus pulposus matter more quickly than a curette. The reamer is usually a cylindrically-shaped, drill-bit-like device with a flat tip and a plurality of sharp edges along its outer sides. The reamer is continuously turned inside the vertebral disk space 121 to scrape the nucleus pulposus matter from the vertebral bones; however, reamers often cause damage to adjacent vertebrae and may cause damage to nerves, blood vessels and/or ligaments while being inserted into the intervertebral space.
The removal of a significant amount of disk material or numerous surgeries often increases the instability of the spine 120 thereby necessitating spinal fusion surgery. In a fusion procedure, a damaged disk may be completely removed. Parts of a bone from another part of the body, such as the pelvis, are harvested, and the bone parts or grafts are subsequently placed between the adjacent vertebrae 100 so that the adjacent vertebrae 100 grow together in a solid mass. In the fusion surgery, which is presently performed as an open surgical technique, the posterior lamina 110 and the centers of the vertebral bodies 106 may both be cut. The surgery often involves consequential damage to the associated posterior ligaments, muscles and joints in addition to the removal of part or all of the lamina 110. The recovery time for a normal spinal fusion surgery is significant due not only to the fact that normal movement cannot be allowed until detectable bone growth has occurred between the bone grafts and the adjacent vertebrae 100, but the associated ligaments, muscles and the location where the bone grafts were harvested must also recover. Oftentimes portions of the spine 120 must be immobilized during the recovery period causing added discomfort and inconvenience to the patient.
What is required, but not presently provided by the prior art devices and methods, is a surgical instrument for performing partial diskectomies that is minimally invasive, easy to use, safe to insert into the body during surgery, provides rapid removal of the nucleus pulposus matter, and which does not cause undesired damage to adjacent vertebrae. What is further required is a micro surgical technique that allows for fast patient recovery times and that can be used on an outpatient basis.
Briefly stated, the present invention comprises a diskectomy instrument. The diskectomy instrument includes an elongate body, at least one blade and a drive stem. The elongate body has a distal end and a proximal end. The elongate body has at least one blade opening proximate the distal end. The at least one blade is removably and movably mounted at least partially within the elongate body proximate the at least one blade opening. The at least one blade has a distal end, a proximal end, at least one sharp edge extending at least partially between the distal end and the proximal end, a ramped portion and a stem mating portion. The drive stem is movably mounted within the elongate body. The drive stem has a distal end, a proximal end and a blade mating portion. The drive stem is configured to slidably engage the at least one blade when the drive stem is moved distally thereby extending the at least one blade radially outward though the at least one blade opening. The blade mating portion is configured to cooperatively engage the stem mating portion of the blade when the drive stem is moved proximally thereby retracting the at least one blade.
The present invention further comprises a diskectomy instrument including an elongate body, a plurality of blades and a drive stem. The elongate body has a distal end and a proximal end. The elongate body has a plurality of blade openings proximate the distal end. The plurality of blades are removably and movably mounted at least partially within the elongate body. Each blade is disposed proximate to a respective one of the plurality of blade openings. The plurality of blades each have a distal end, a proximal end, at least one sharp edge extending at least partially between the distal end and the proximal end, a ramped portion and a stem mating portion. The drive stem is movably mounted within the elongate body and has a distal end, a proximal end and a blade mating portion. The drive stem is configured to slidably engage each of the plurality of blades when the drive stem is moved distally thereby extending the plurality of blades radially outward though the respective plurality of blade openings. The blade mating portion is configured to cooperatively engage the stem mating portion of each of the plurality of blades when the drive stem is moved proximally thereby retracting the plurality of blades.
The present invention further comprises a diskectomy blade having a distal end and a proximal end for use in a diskectomy instrument. The diskectomy instrument includes a drive stem having a blade mating portion. The blade includes at least one sharp edge, a ramped portion and a stem mating portion. The at least one sharp edge extends at least partially between the distal end and the proximal end. The ramped portion is configured to slidably engage one of the drive stem and the body of the diskectomy instrument. The stem mating portion is configured to couple with the blade mating portion of the diskectomy instrument.
The present invention further comprises a method of using a diskectomy instrument. The diskectomy instrument includes an elongate body having a blade opening, a blade having a sharp edge, a ramped portion and a stem mating portion. The diskectomy instrument also includes a drive stem having a blade mating portion. The drive stem is configured to slidably engage the at least one blade when the drive stem is moved distally thereby extending the blade radially outward though the blade opening. The blade mating portion of the drive stem is configured to cooperatively engage the stem mating portion of the blade when the drive stem is moved proximally thereby retracting the blade. The method includes the step of moving the drive stem proximally causing the blade mating portion to engage the stem mating portion of the blade thereby retracting the blade at least partially into the elongate body. The method also includes the steps of inserting a distal end of the diskectomy instrument into a small gap between a first vertebra and a second vertebra of a spine and moving the drive stem distally causing the blade mating portion to engage the blade which in turn moves the blade distally and radially outward. The method further includes the steps of rotating the blade in a cutting direction defined by the orientation of the sharp edge and moving the drive stem proximally causing the blade mating portion to engage the stem mating portion of the blade thereby retracting the blade at least partially into the elongate body. The method further includes the step of withdrawing the distal end of the diskectomy instrument from the small gap.
The present invention further comprises a method of using a diskectomy instrument and a working tube in outpatient surgery. The diskectomy instrument includes an elongate body having a blade opening, a blade having a sharp edge and a partially convex shape, a ramped portion and a stem mating portion. The diskectomy instrument also includes a drive stem having a blade mating portion. The drive stem is configured to slidably engage the at least one blade when the drive stem is moved distally thereby extending the blade radially outward though the blade opening. The blade mating portion is configured to cooperatively engage the stem mating portion of the blade when the drive stem is moved proximally thereby retracting the blade. The method includes the step of moving the drive stem proximally causing the blade mating portion to engage the stem mating portion of the blade thereby retracting the blade at least partially into the elongate body. The method also includes the steps of inserting a distal end of the working tube proximate a small gap between a first vertebra and a second vertebra of a spine accessible through an incision between about 10 mm and about 100 mm in span and inserting a distal end of the diskectomy instrument into the working tube in order to access the intervertebral space between the first and second vertebrae. The method includes the steps of moving the drive stem distally causing the drive stem to engage the blade which in turn moves the blade distally and radially outward and rotating the blade in a cutting direction defined by the orientation of the sharp edge so that the convexly-shaped blade finds the most concave portions of the first and second vertebrae. The method includes the steps of moving the drive stem proximally causing the blade mating portion to engage the stem mating portion of the blade thereby retracting the blade at least partially into the elongate body and withdrawing the distal end of the diskectomy instiument from the working tube.